PCB Material of RoHS Compliant Products

While working on a project for the UK market, the issue of Printed Circuit Board material came up. As this product was required to be RoHS compliant (Restrictions of Hazardous Substances Directive), it must be able to withstand the higher re-flow temperatures associated with lead free soldering, which can peak at 260C.
A common misconception with this is that using just a higher TG (Glass Transition Temperature) will be acceptable. However, you will also need to ensure your base material is also of a higher TD (Decomposition Temperature).
The TG value is where the resin changes from rigid to soft material and TD is the value where the material weight changes by 5%. Exceeding the TD value will cause permanent damage to the circuit board, which can result in loss of adhesion and delamination.
See the link below for a more detailed and in depth read.
www.isola-group.com/images/media/ReengineeredFR4Materials.pdf
So when selecting PCB material for the lead free solder process, a good guide is to use material with TD above 340C and TG above 170C.